|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
Development, Vol 117, Issue 1 177-189, Copyright © 1993 by Company of Biologists
JOURNAL ARTICLES |
L Gleizer and GS Stent
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Segmentation in the leech embryo is established by a stereotyped cell lineage. Each of the 32 segments arises from homologous, bilaterally symmetrical complements of mesodermal and ectodermal blast cell clones. Although segments are homologous, they are regionally differentiated along the longitudinal body axis. Various segments display idiosyncratic ensembles of features, which constitute discrete segmental identities. The differentiation of segment-specific features, such as the mesoderm-derived nephridia, genital primordia and identified Small Cardioactive Peptide immunoreactive neurons, reflects a diversification of the developmental fates of homologous blast cell clones. We have investigated whether segment-specific differentiation of homologous mesodermal blast cell clones depends on cell-intrinsic mechanisms (based on the cells' lineage history) or on cell-extrinsic mechanisms (based on the cells' interactions with their environment) in embryos of Theromyzon rude. For this purpose, we first mapped the segment-specific fates of individual mesodermal blast cell clones, and then induced mesodermal clones to take part in the formation of segments for which they are not normally destined. Two types of ectopic segmental position were produced: one in which a mesodermal blast cell clone was out of register with all other consegmental cells and one in which a mesodermal blast cell clone was out of register with its overlying ectoderm, but was in normal register with the mesoderm and ectoderm on the other side of the embryo. Mesodermal blast cell clones that developed in either type of ectopic segmental position gave rise to segment-specific features characteristic of their original segmental fates rather than their ectopic positions. Thus, the development of segmental identity in the leech mesoderm is attributable to a cell-intrinsic mechanism and, either before or soon after their birth, mesodermal blast cells are autonomously committed to segment-specific fates.
This article has been cited by other articles:
|
|
 |
|
  S. O. Zhang and D. A. Weisblat Applications of mRNA injections for analyzing cell lineage and asymmetric cell divisions during segmentation in the leech Helobdella robusta Development, May 1, 2005; 132(9): 2103 - 2113. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Shain, D. Stuart, F. Huang, and D. Weisblat Segmentation of the central nervous system in leech Development, January 2, 2000; 127(4): 735 - 744. [Abstract] [PDF]
|
|
|
|
|
|
J. Nicolas, L Mathis, C Bonnerot, and W Saurin Evidence in the mouse for self-renewing stem cells in the formation of a segmented longitudinal structure, the myotome Development, January 9, 1996; 122(9): 2933 - 2946. [Abstract] [PDF]
|
|
|
|
|
|
F. Huang and D. Weisblat Cell fate determination in an annelid equivalence group Development, January 6, 1996; 122(6): 1839 - 1847. [Abstract] [PDF]
|
|
|
|
|
|
D Nardelli-Haefliger, A. Bruce, and M Shankland An axial domain of HOM/Hox gene expression is formed by morphogenetic alignment of independently specified cell lineages in the leech Helobdella Development, January 7, 1994; 120(7): 1839 - 1849. [Abstract] [PDF]
|
|
|
|
|
|
D Nardelli-Haefliger and M Shankland Lox10, a member of the NK-2 homeobox gene class, is expressed in a segmental pattern in the endoderm and in the cephalic nervous system of the leech Helobdella Development, January 7, 1993; 118(3): 877 - 892. [Abstract] [PDF]
|
|
